Technical Field
The invention relates to sensors for wheel end assemblies, and in particular to sensors for wheel end assemblies of heavy-duty vehicles, such as tractor-trailers. More particularly, the invention is directed to a wireless sensor for a wheel end assembly of a heavy-duty vehicle, which is mounted in a hub cap of the wheel end assembly. The sensor is thus located in a protected, yet easily-accessible environment, is independent from the vehicle power supply, and detects operating conditions of the heavy-duty vehicle, such as temperature, vibration, moisture, and/or other parameters. The sensor includes convenient indicating means, while being capable of accommodating components of a tire inflation system.
Background Art
For many years, the heavy-duty vehicle industry has utilized wheel end assemblies which are mounted on each end of one or more axles. Each wheel end assembly typically includes a wheel hub rotatably mounted on a bearing assembly that in turn is immovably mounted on the outboard end of the axle, commonly known as an axle spindle. The bearing assembly includes an inboard bearing and an outboard bearing, which may be separated by a bearing spacer. An axle spindle nut assembly secures the bearing assembly on the axle spindle by threadably engaging threads that are cut into the outer diameter of the outboard end of the axle spindle. In addition to retaining the position of the bearings and any spacer, the axle spindle nut assembly may be used to provide a clamp force to compress the bearings, and any bearing spacer, to a predetermined level.
As is well known to those skilled in the art, for normal operation of the wheel end assembly to occur, the bearing assembly and surrounding components must be lubricated with grease or oil. Therefore, the wheel end assembly also must be sealed to prevent leakage of the lubricant, and also to prevent contaminants from entering the assembly, both of which could be detrimental to its performance. More specifically, a hubcap is mounted on an outboard end of the wheel hub adjacent to and outboard from the axle spindle nut assembly, and a main seal is rotatably mounted on an inboard end of the hub and the bearing assembly in abutment with the axle spindle, resulting in a closed or sealed wheel end assembly.
While most wheel end assemblies include these general features, the design and arrangement of the hub, bearing assembly, hubcap, main seal, and other components, as well as the axle spindle, vary according to the specific vehicle design and its anticipated uses. In addition, it has been desirable to sense and monitor operating conditions of the wheel end assembly in order to determine if issues with any of the wheel end assembly components have arisen. For example, it has been desirable to monitor the temperature of the wheel end assembly, as a consistently high temperature may indicate a lack of lubricant or improper functioning of the bearing assembly. It has also been desirable to monitor the vibration experienced in the wheel end assembly, as a consistently high level of vibration may also indicate improper functioning of the bearing assembly.
In the event that undesirable levels of the sensed operating conditions occurs, it may be possible to stop operation of the vehicle and/or perform maintenance on the vehicle to repair or replace problematic wheel end components before failure of those components takes place. When failure of a wheel end component occurs, there may be damage to surrounding components, which greatly increases the cost and the time to repair the wheel end assembly. Thus, when the vehicle can be stopped and/or components can be replaced before failure occurs, it may be possible to significantly reduce the cost and the time that is required to repair the wheel end assembly.
In the prior art, sensors for wheel end assemblies have been employed, but possess certain disadvantages. For example, some prior art sensors were externally mounted, that is, mounted on the outside of a wheel of the wheel end assembly. Because the exterior of a wheel end assembly experiences extremely harsh conditions during operation of the vehicle, such as road hazards and corrosive anti-icing chemicals, the externally-mounted sensors have been undesirably prone to significant damage. In addition, externally-mounted sensors are subject to rough handling during disassembly and reassembly of the wheel end assembly for servicing, which may also damage the sensor.
As an alternative, other prior art sensors have been mounted inside of the wheel end assembly. However, it is necessary for the sensor to communicate or otherwise transmit the data for the conditions that are being monitored, which is difficult to do from inside a wheel end assembly. More particularly, the rotation of the wheel hub about the axle spindle and the significant amount of metal employed in the hub, spindle, bearings, and other components, interferes with wireless signal transmission. As a result, many internally-mounted sensors have used wires that extend inside the axle to transmit data. Because such wires must travel through areas of the vehicle that are exposed to corrosive elements, the wires often corrode easily, which undesirably disables communication from the sensor. Such wires are also subject to scuffing and physical wear from vibration experienced during operation of the vehicle, which may undesirably cause the wires to short out.
Many prior art sensors that have been mounted inside of the wheel end assembly are electrically connected to the vehicle power supply and thus depend upon the vehicle power supply to operate. For example, in the case of a tractor-trailer, prior art sensors have been connected to the tractor power supply. It is known in the art that connections to the vehicle power supply often encounter difficulty in adequately providing sufficient power on a consistent basis to enable a sensor to operate, due to the harsh environment surrounding the connection of the sensor to the vehicle power supply. As a result, such prior art sensors have experienced difficulty in maintaining a desired ability to continuously operate while the vehicle is traveling.
In addition, many prior art sensors that have been mounted inside of a wheel end assembly are not easily accessible. In the event that such a sensor needs to be adjusted, repaired, or replaced, the sealed wheel end assembly must be opened and sometimes partially disassembled to access the sensor. Opening and partially disassembling a sealed wheel end assembly is undesirable, as contaminants may enter the wheel end assembly, which may reduce the performance and/or life of the wheel end assembly. Also, due to the precise requirements for proper assembly of wheel end components, any disassembly that is needed to access a sensor is undesirable, as it is possible for components to be re-assembled in an inferior manner, which again reduces the performance and/or life of the wheel end assembly.
Moreover, the space that is available inside of a wheel end assembly for a sensor or other components is extremely limited. Many prior art sensors that have been mounted inside of a wheel end assembly take up a significant amount of space, which often interferes with or prevents the installation of other components, such as components of a tire inflation system. Because tire inflation systems provide advantages associated with automatic monitoring and control of tire pressure through methods and structures that are known in the art, it is desirable to accommodate components of tire inflation systems.
Such disadvantages of the prior art make it desirable to develop a sensor for a wheel end assembly of a heavy-duty vehicle that is mounted in a protected environment, is independent from the vehicle power supply, includes wireless data communication or transmission, is easily accessed for servicing, provides effective and efficient means for communicating or transmitting data, and accommodates components of a tire inflation system. The present invention satisfies these needs, as will be described below.